Ablation of myocardial tissue is well known as a treatment for cardiac arrhythmias. In radio-frequency (RF) ablation, for example, a catheter is inserted into the heart and brought into contact with tissue at a target location. RF energy is then applied through an electrode on the catheter in order to create a lesion for the purpose of breaking arrhythmogenic current paths in the tissue.
Recently, circumferential ablation of the ostia of the pulmonary veins has gained acceptance as a treatment for atrial arrhythmias, and particularly for atrial fibrillation. For example, U.S. Pat. No. 6,064,902 describes a catheter for ablating tissue on the inner wall of a blood vessel, such as a pulmonary vein. The tip portion of the catheter is deflectable from a first, generally straight, configuration, in which the proximal and distal sections are substantially co-linear, to a second, J-shaped, configuration in which the proximal and distal sections are generally parallel with a separation therebetween substantially corresponding to the inside diameter of the blood vessel. The distal end portion of the catheter is rotated about the longitudinal axis of the catheter to cause a circumferential displacement of proximal and distal ablation electrodes on the catheter along the inner wall of the pulmonary vein. In this way, the electrode catheter may be used to ablate a number of circumferentially-spaced sites on the inner wall of the pulmonary vein by ablating one or two sites at each circumferential position.
U.S. Patent Application Publication 2005/0033135, whose disclosure is incorporated herein by reference, describes a lasso for pulmonary vein mapping and ablation. A catheter for circumferentially mapping a pulmonary vein (PV) includes a curved section shaped to generally conform to the shape of the interior surface of the PV. The curved section comprises one or more sensing electrodes, and its proximal end is joined at a fixed or generally known angle to a base section of the catheter. Position sensors are fixed to the curved section of the catheter and to the distal end of the base section. The catheter is inserted into the heart, and the curved section is positioned in contact with the wall of the PV, while the base section remains within the left atrium, typically positioned such that the joint with the curved section is at the ostium of the vein. The information generated by the three position sensors is used to calculate the locations and orientations of the sensing electrodes, which enables mapping of the surface of the PV. The sensing electrodes may additionally perform ablation of selected sites, or the catheter may further comprise ablation elements.
U.S. Patent Application Publication 2010/0168548, whose disclosure is incorporated herein by reference, describes a lasso catheter for use in a system for electrical mapping of the heart. The catheter has an array of raised, perforated electrodes, which are in fluid communication with an irrigating lumen. There are position sensors on a distal loop section and on a proximal base section of the catheter. The electrodes are sensing electrodes that may be adapted for pacing or ablation. The raised electrodes securely contact cardiac tissue, forming electrical connections having little resistance.
U.S. Patent Application Publication 2011/0160719, whose disclosure is incorporated herein by reference, describes a catheter with an arcuate end section. The end section is formed so as to define, when unconstrained, an arc oriented obliquely relative to the axis of the catheter shaft and having a center of curvature on the axis. One or more electrodes are disposed at respective locations along the end section. In some embodiments, these electrodes include a tip electrode extending over the tip and a plurality of proximal electrodes distributed along the end section. The end section is configured so that when the unconstrained end section is advanced axially against a tissue surface in the body, the end section engages the tissue surface along the arc so that the tip electrode and at least some of the proximal electrodes contact the tissue surface simultaneously. Optionally, the end section includes one or more joints, which can be straightened and steered so as to bring the tip electrode alone into contact with the tissue surface.